The present invention relates to generally an optical image reader and more particularly a light source for an optical information reading device with a self-scanning type array of light receptors.
In general tungsten halogen lamps and fluorescent lamps are used as a light source for the optical image readers.
The tungsten halogen lamp may produce highly brilliant light, but dissipates a considerable quantity of heat so that the power consumption is high and accordingly the conversion efficiency is unsatisfactorily low. The fluorescent lamp dissipates less heat so that its conversion efficiency is high, but its light output per unit of length is less as compared with the tungsten halogen lamp so that when it is used as a light source for an optical image reader, the exposure time inevitably becomes longer. In the case of an optical image reader of the type having a head consisting of a self-scanning type array of light receptors, the charge accumulation due to dark current in the light receptor increases, resulting in the degradation of the signal-to-noise ratio S/N and in an unsatisfactorily slow reading speed.